Calibration and Validation of Metop/ATOVS and AVHRR products. Éamonn McKernan (Rhea System S. A.)

Transcription

1 Calibration and Validation of Metop/ATOVS and AVHRR products Éamonn McKernan (Rhea System S. A.) François Montagner, Dieter Klaes, Peter Schlüssel, Yves Buhler (EUMETSAT) With contributions from John Jackson, Mike Elson and Maria Capellades ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 1

2 Outline Objectives and priorities Approach Tools Cal/Val Facility User Tools Activities Initial checkout Campaign(s) Analyses Monitoring Scheduling ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 2

3 Objectives Generate validated products in a timely manner to meet user requirements and achieve the overall mission objectives... AND... achieve state-of-the-art performance and accuracy from the EPS instruments and their generated data products. Meeting these objectives involves: Converting raw instrument data into geo-located products expressed in terms of recognised physical units testing and revision of processing algorithms and required databases determination of the product quality, in terms of precision and accuracy guaranteed over the mission lifetime assessed by multiple independent means cross-checked against similar instruments ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 3

4 Priorities (1): drivers Criteria for prioritising Validation Activities: Objective activity selection criteria include product priority, accuracy requirements, cost and feasibility. More Subjective criteria include geographic coverage, temporal coverage and instrument type. Outputs quantitative error estimates, characterising the products recommendations for auxiliary data changes processor changes further (operational) monitoring/validation ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 4

5 EURD Product Priorities (objective requirement) Priority 1 Radiances / Brightness temperatures (0.25K) Temperature sounding (1K) Relative humidity sounding (5%) Cloud cover (5%) Cloud top temperature (1K) Priority 2 Cloud liquid water path (0.01 mm) Cloud top height (200m) Priority 3 SST (0.4K), NDVI, LST (1K) ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 5

6 Approach: Calibration Most instruments are calibrated by viewing warm and cold targets. Nonlinearity corrections are applied for some channels based upon pre-launch data. Visible/near-infrared channels are calibrated based upon prelaunch values until sufficient surface data are collected (1+ years). Aerosol retrievals may provide further information about the calibration of the vis/nir channels. Spectral calibration will initially be based upon pre-launch measurements, but post-launch data may be employed for adjustments once initial checks have been completed. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 6

7 Approach: Validation Validation consists primarily of assessment and monitoring of processing (thresholds, processing options, etc.), mostly through comparisons focus on large, well-understood, operational datasets sondes, buoys, NWP, AMDAR, other satellites, etc. + case studies using specialised instrumentation spectrometers, radiometers, aircraft, ships, stratospheric balloons, etc. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 7

8 Calibration and Validation Facility A Calibration and Validation Facility has been procured for Core Ground Segment product analyses. PCs with Linux / IDL and ENVI. Stores 1 month s Metop data, and has access to the EUMETSAT archive for retrieving archived data and reports. Customised functionality for reading formatted datasets, generating standardised displays, performing anticipated investigations (geolocation modelling, finding collocations, interpolations, etc.), scheduled reporting. Flexible and programmable to adapt to future needs. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 8

9 User Tools EUMETSAT is eager to hear from the users about any issues that they may discover when using the products. To facilitate such analysis, a number of tools will be made available to the user community. Tool and product format information is available at: There are three classes of user tools: IDL-based The IDL tools can be run without a license using the IDL virtual machine ( but in this environment do not offer significantly more functionality than the standalone tool. standalone misc. related tools ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 9

10 The EPS Product Reader IDL tools Can read the whole EPS product into memory. Can read specific product fields and store pointers to these records/fields in the product object. Is needed for EPSMapper and EPSiPlotter. EPSMapper Can visualise data onto a map projection selected by the user. EPSiPlotter Provides predefined product-specific visualisations for the product to permit more detailed analyses. These tools are designed for users familiar with IDL programming. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 10

11 The EPSView tool Standalone tool Can generate two-dimensional or geolocated images of product parameters It provides for a tree-like drill-down into the full product The product can be viewed down to the bit level, if desired. EPSView was designed to operate in a standalone mode (Java-based) and to be easy to use. All of these tools are or will be shortly available on the EUMETSAT external website before launch. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 11

12 noaa2eps Additional Related tools Convert NOAA L1b products into EPS format products. If people need additional EPS format ATOVS products prior to launch they can use this tool to generate them. Kai Can be used to combine PDUs into full products, e.g. in an NRT terminal. Eugene Can be used as a command line product reader, or built as a library to access EPS products from C++ and Python. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 12

13 Activities (I) The initial instrument checkout will be completed by ESA before Cal/Val begins (6 weeks). An initial product checkout will be carried out against range limits, looking for visual anomalies, etc. Trending of instrument characteristics and product parameters will be carried out for monitoring purposes. NWP data will be employed for monitoring purposes. Outliers will be flagged for visual inspection on a daily basis to identify sudden changes in the products (or validation datasets). ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 13

14 Activities (II) A campaign will be carried out using extra radiosonde launches timed to coincide with Metop overpasses. The sites have not yet been selected, but preference will be given to those with nearby correlative measurements. Globally distributed measurements from operational networks (radiosondes, buoys and aircraft) will be matched against the products. Additional analyses will be carried out using smaller high quality and high resolution datasets to improve confidence in the data, and to validate remaining products. Results from the Research Announcement of Opportunity will also be analysed. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 14

15 Product Example: Temperature sounding Radiosondes will provide the primary validation. Operational network Additional launches NWP will be used to monitor the product for changes. NOAA measurements will be compared Aircraft/balloon FAAM (TBC Opportunistic) IASI balloon dropsondes/sdla (TBC Opportunistic) Other satellites AIRS TES, etc...? ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 15

16 Method Example: NWP NWP provide a global, well understood dataset that will be analysed daily. Radiances (RTTOV-7) Temperature and humidity soundings SST, LST 12 hour forecasts will be employed. NWP to be interpolated to measurement space. Preference given to NWP in the vicinity of sondes. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 16

17 Day-2 activities After initial product behaviour has been established, a more rigorous analysis may be applied to resolve uncertainties inherent in comparing retrieved quantities (Rodgers and Connor 2002). Spectral response profiles may be shifted in response to post-launch modelling efforts. Once validated, IASI data will be employed for additional comparisons of radiances and geophysical products. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 17

18 ATOVS Schedule AVHRR is critical to subsequent validation activities. AVHRR Geolocation will be validated first, then AVHRR Cloud mask then geolocation and collocation of ATOVS instruments Temperature and water vapour profiles are of highest priority for validation. Radiosondes NWP NOAA platform instruments other datasets as secondary priority ground-, water-, air-, and space-based Dry runs will be carried out before launch for Mandatory and Important activities using NOAA data. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 18

19 Generic Sequencing Instrument switch-on and initial testing Set instrument operational configuration Instrument monitoring, troubleshooting Stable level 0 data Initial calibration (instrument dependent) Stable level 1 product Level 1 monitoring, validation, refined calibration Level 1 product within spec Level 1 monitoring, validation, refined calibration Improved Level 1& 2 products Level 2 monitoring, validation, tuning Level 2 monitoring, validation, tuning Level 2 product within spec ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 19

20 Summary The EUMETSAT Cal/Val Facility has been procured to calibrate and validate EPS products. The commissioning phase is currently scheduled to last the first 6 months following the launch. Validation will rely heavily on the use of large, well understood datasets, complemented by more detailed analyses where practical. Tools are available to the user community for independent analyses, and additional input has been solicited through the RAO mechanism. ITSC May 2005 Beijing, China EUM.EPS.SYS.RPT Slide 20